Method of making expandable member for forming seals and applying force

ABSTRACT

An expandable member is disclosed that includes a molded body of elastomeric material with a core embedded therein. At least a portion of the core is not bonded to the body. A fluid conduit is provided through which fluid can be injected between the core and the unattached portion of the body to move the core and the unattached portion apart and expand the member.

This is a division of application Ser. No. 684,835, filed May 10, 1976,now abandoned.

This invention relates generally to members that are expanded by fluidpressure to form seals, transmit force, and the like.

The expandable member of this invention has many uses. There are manyapplications for an expandable member having a body that can be moldedto any desired shape with a cavity that is formed therein during themolding process that has a pre-selected size, shape, and location, andit is an object of this invention to provide such a member and a methodof making the same.

One use for the member of this invention is in the isostatic moldingprocess where granular or powdered material is compacted to the desiredshape. It is very important that the material be subjected to asubstantially uniform compressive force. In the past, membranes havingrelatively thin walls were used. The membranes encircled the material tobe compacted and were generally open-ended cylinders. Pressure on theoutside forced the membranes against the material with the desiredcompacting pressure. The pressure fluid was confined to act against theoutside of the membrane by holding the ends of the membrane in sealingengagement with the mode body. As the compacting pressures increase, itbecomes more and more difficult to keep the pressure fluid from leakingaround the ends of the membrane.

It is another object of this invention to provide an expandable memberfor use in an isostatic compacting press having a molded body with aninternal cavity that is connected to a source of pressure fluid througha conduit thereby eliminating the need to maintain a seal between themember and the body of the press.

It is another object of this invention to provide an expandable memberfor an isostatic press having a molded body that can be shaped tocompact the material to the desired configuration.

It is another object of this invention to provide an expandable memberfor an isostatic press having a molded body that can be provided with apre-selected wall thickness around the cavity that will confine thepressure to be applied thereto while allowing the desired expansion ofthe member.

Another application of the expandable member of this invention is forsealing between adjacent surfaces. There are two general types of sealmembers, compression energized and pressure energized. The first typemust be designed originally to have sufficient compression that wheninstalled to maintain a seal against the maximum pressure differentialexpected in service. The pressure energized seal theoretically willincrease the sealing pressure directly as the pressure increases. It isan object of this invention to provide an expandable member for use ascompression type seal that allows the compressive force exerted by themember on the sealing surface to be controlled by a second source ofpressure fluid so that such force can be varied as required by thepressure differential across the seal.

These and other objects, advantages, and features of this invention willbe apparent to those skilled in the art from a consideration of thisspecification, including the attached drawings and appended claims.

In the drawings:

FIG. 1 is a sectional view through a mold in which the expandable memberof this invention has been constructed in accordance with the method ofthis invention;

FIG. 2 is a sectional view through an isostatic mold using theexpandable member formed in the mode of FIG. 1 to apply pressureisostatically to a granulated mass of material;

FIG. 3 is a partial sectional view of the press of FIG. 2 showing theexpandable member applying pressure to compact the material to thedesired shape;

FIG. 4 is a view similar to FIG. 3 of the press of FIG. 2 showing theremoval of the compacted material from the press;

FIGS. 5 and 6 show the expandable member of this invention adapted tocompact granulated material into the shape of a valve seat;

FIGS. 7 and 8 show the arrangement whereby the expandable member of thisinvention is arranged to compact granulated material on the outside of avalve disc;

FIG. 9 is a vertical sectional view of a housing for enclosing athreaded connection between two tubular members with the expandablemember of this invention arranged to provide a seal between the sectionsof the housing and between the housing and the tubular members to allowthe connection to be tested by external pressure;

FIG. 10 is a sectional view taken along line 10--10 of FIG. 9:

FIG. 11 is a sectional view taken along line 11--11 of FIG. 9;

FIG. 12 is an isometric view of the two seal members used in theembodiment of FIGS. 9, 10 and 11;

FIG. 13 is a sectional view through an alternate embodiment of theexpandable member of this invention; and

FIGS. 14, 15 and 16 are views similar to FIG. 13, with the membersubjected to increasing the internal pressure.

The mold of FIG. 1 is designed to provide the desired shape to anexpandable member constructed in accordance with the method of thisinvention for use in an isostatic press. In fact, in this embodiment,part of the mold is also part of the press. The mold includes annularmember 10 having inwardly extending lower flange 11. Tubular member 12comprises the inside portion of the mold and is notched on its lower endto be centered by the upper edge of flange 11. Between outer tubularmember 10 and inner tubular member 12 is annular space 14 in which thebody of elastomeric material will be molded to the desired shape. Inthis case, the shape is annular.

Located in space 14 is annular core 15. In accordance with thisinvention, core 15 is made of a material or is coated with a materialthat will keep the elastomeric material of the body from bonding orattaching itself to at least a portion of the surface of the core.Preferably, the core is made of a material having sufficient structuralstrength to be self-supporting. The material for the core can be chosenfrom the plastics, such as nylon, polyethylene, and polypropylene, orfrom the metals, such as aluminum or steel. If the material used for thebody would tend to bond to the core material, the core, or that surfaceto which the body is not to bond, may be coated with a releasing agent,such as the soap solutions or silicon base liquids that are commonlyused in rubber molds and the like.

The core is embedded in the elastomeric material of the member,therefore it is supported in mold cavity 14 in the desired positionbefore the mold is filled with the material to form the body of theexpandable member. In the embodiment shown in FIG. 1, core 15 has aplurality of openings 16, only one of which is shown in the figure,spaced around the core. Threaded centering pins 17 are mounted in tappedholes around outer mold member 10 with their tapered ends engaging holes16 to support and center the core in the mold cavity. The centering pinsinclude unthreaded sections 18 that carry seal rings 19 to seal betweenthe centering pins and the mold body to keep the elastomeric materialfrom escaping during the molding operation. Threaded sections 20 thatengage tapped portions 21 of the openings allow the pins to be adjustedto center the core. Locknuts 22 hold the pins in the desired position.

With the core firmly held in the mold cavity, the cavity can be filledwith elastomeric material to form body 24 of the expandable member. Themold shown in FIG. 1, is designed to use an elastomeric material thatcan be placed in the mode cavity as a liquid, after which it will cureinto a solid rubber-like material. For services as a part of acompacting press, polyurethane is the preferred material for the body ofthe expandable member. This material can be mixed with a curing agent asa liquid, poured into the mode cavity up to the level desired, afterwhich, it will cure into a solid elastomeric material having goodproperties for use as the compacting force transmitting member of acompacting press.

As explained above, a cavity is formed in the molded body during themolding operation. This is accomplished by providing core 15, which atleast a portion of the surface thereof will not bond to the elastomericmaterial of the body. In the expandable member, being made in FIG. 1,the inner portion of the elastomeric body will move inwardly to compactthe material in the press. Therefore, in this embodiment the innersurface of annular core 15 should be of such a material, or coated withsuch a material, that the body of elastomeric material will not bond orattach itself to the inner surface of the core. Since there is no bondbetween inner surface 15a and body 24 of elastomeric material, a cavityexists between the unattached portion of body 24 adjacent the innersurface of core 15. By supplying fluid under pressure into this cavityor potential cavity, the unattached portion of the body can be forcedaway from the core to expand the member.

The space between the core and the adjacent unattached portion of thebody of the member may be substantially non-existant, since, beforehaving been expanded the unattached portion may well be in contact withthe core. In this respect, the cavity may be better described as apotential cavity that will exist when the unattached portion is forcedaway from the core. Once expanded, the unattached portion will probablynot return to the same intimate contact with the core and a cavity willexist thereafter. As used in this specification, "cavity" is intended tomean both existing and potential spaces.

Conduit means are provided through which fluid under pressure can besupplied to force the unbonded or unattached portion of the body and thecore apart to expand the member. In the embodiment shown in FIG. 1,outer annular member 10 of the mold has tapped opening 26 extendingthrough the member. This tapped opening is of two diameters. The inner,smaller diameter portion 26a is provided with straight threads, whereasthe outer portion 26b is tapped for tapered pipe threads. Before thebody of elastomeric material is molded, threaded nipple 27 is threadedto straight thread section 26a. The nipple includes an unthreadedportion 27a that extends into opening 28 through the core. A solid pipeplug is connected to the tapered thread section to seal the opening.

The mold cavity is then filled with the elastomeric material, which, asexplained above, in this embodiment is initially liquid. After thematerial has cured into a solid body of elastomeric material, it will bebonded to and in sealing engagement with the exposed portion of threadednipple 27 as well as the inside wall surface of housing or annularmember 10. The pipe plug is removed and the body material is drilled outof nipple 27. A conventional pipe nipple can now be connected to outerportion 10 of the mold and fluid under pressure can flow throughthreaded nipple 27 and into the cavity formed between the core surface15a and body 24 of elastomeric material.

As shown in FIG. 1, inside surface 15a of the core can be provided withspaced parallel circular grooves 19 that intersect transverse groove 23which connects grooves 19 to the outlet of nipple portion 27a. Such anetwork of grooves will allow the pressure fluid to be quickly spreadaround the inside surface of the core while expanding. They also providereturn paths when the member is contracting and forcing the fluid out ofthe cavity. To keep the grooves from being filled during the moldingoperation, they may be filled with a solid or semi-solid material thatcan be dissolved or washed from the grooves after the elastomericmaterial has cured.

As stated above, the particular expandable member molded or cast in themode of FIG. 1 is designed for use in an isostatic press. Thisarrangement is shown in FIG. 2. After the elastomeric material hascured, inner mold member 12 is removed and certain maching operationsare conducted on outer mold member 10 to prepare it for use in thepress. These consist of cutting threads 30 at the upper end of the moldbody and cutting an annular groove 31 in flange portion 11 of the body.Cap ring 32 is connected to the body through threads 30 to confine theupper end of the expandable member. This leaves only the inner surfaceof the member free to move when the cavity inside the member is suppliedwith fluid under pressure. Annular groove 31 in flange 11 receivesannular ring 33 which, as will be explained below, is used to push thecompacted material out of the press.

The other parts of the press shown include mandrel 34 which is generallycylindrical in shape and extends through the opening of flange 11 toprovide the inner surface against which the material will be compacted.Flange 35 is attached to mandrel 34 and in turn to body 10 of the pressby machine screws 36. Cavity 37 between the mandrel and the expandablemember receives material 38 to be compacted. This material is powderedor granular material, such as tungsten carbide or one of thefluorocarbons. After cavity 37 is filled with granular material 38, ram39 moves annular closure member 40 into the position shown in FIG. 2 toclose the upper end of cavity 37.

At this point in the operation of the press, everything is ready toapply pressure isostatically to the material to compact it the desiredamount. As explained above, a conduit, such as tubing 42, is connectedto tapped portion 26b of body 10 and fluid under pressure can besupplied to cavity 43 between the unattached portion of body 24 and core15 to cause the member to expand. This action is shown in FIG. 3, wherethe fluid has forced portion 24a of the body of elastomeric materialaway from core 15 and in doing so has exerted an isostatic pressure ongranulated material 38, compacting this material against the outersurface of mandrel 34. In this compacting operation, the elastomericmaterial of the expandable member can expand only in the directiontoward the granulated material. It is confined in all other directions.As the pressure builds up inside cavity 43 between the core and theunattached portion of the body, the elastomeric material will act moreand more like a fluid and transmit the fluid pressure uniformly againstthe granulated material in the press. This is the great advantage ofisostatic molding processes in general and it is also obtained using thenovel expandable member made in accordance with the method of thisinvention. In FIG. 4, pressure has been released from cavity 43 and ring33 is pushing the tube of compacted granulated material from the pressafter the ram has moved the upper retaining member 40 upwardly and outof the way. Ring 33 is moved by a plurality of rods 44, only one ofwhich is shown, that extends through aligned openings 45 and 46 inflanges 35 and 11, respectively.

In FIGS. 5 through 8, two additional mold arrangements are shown thatuse different shapes of the expandable member of this invention. InFIGS. 5 and 6, a mold is designed employing the expandable member ofthis invention to form a valve seat for a butterfly valve out of one ofthe fluorocarbons. In FIGS. 7 and 8, a mold is provided for coating theoutside surface of the disc of a butterfly valve with a fluorocarboncoating.

The press of FIGS. 5 and 6 includes two expandable members 50 and 51.They include bodies of elastomeric material 50a and 51a, in which areembedded cores 50b and 51b, respectively. The two members combine toform a complete ring around cavity 52 in which granulated or poweredmaterial is placed to be compacted. Each member is located in one halfof split mold 53 and the members encircle mandrel 54 which comprises twopieces 54i a and 54b that are designed to allow the finished product,the valve seat, to be removed from the mold after the molding operation.Portion 54a of the mandrel is an integral part of outer ring 55 whichholds the two halves of the mold in position during the moldingoperation. The two halves of the mold are forced together by the wedgingaction of tapered outer surfaces 56 and 57 of the mold halves andtapered inner surface 58 of ring 55. The ring is held in place by bolts59. Holes 55a in the ring allow the conduits (not shown) for thepressure fluid to be connected to passageways 50c and 51c to supplypressure to expand the members and compress the granular material incavity 52. Passageways 50c and 51c are drilled through bodies 50a and51a after they are molded. The bodies are bonded to the inside surfaceof split mold 53 to confine the fluid to the passageways.

In FIGS. 7 and 8, expandable members 60 and 61 made in accordance withinvention, are designed to compact coating 63 of granular material onthe outer surface of a butterfly valve disc. The members include bodiesof elastomeric material 60a and 61a with cores 60b and 61b embeddedtherein. Each member shown in FIG. 8 is shaped to enclose one half ofdisc 62. In FIG. 7, the ends of member 61 are shown with the shape ofthe core shown by dotted lines. The abutting ends of the members act toconfine circumferential expansion and combine with the mold body tolimit expansion except in the direction of the granulated material. Asbefore, the pressure of the fluid supplied between the cores and theinner portion of the bodies of the members through conduits 64 and 65and passageways 66 and 67 will be transmitted through the elastomericmaterial substantially uniformly over the entire surface beingcompressed at the operating pressure of the mold to provide a uniformlayer of compacted material over the outside of the valve disc.

In the embodiments described above, the expandable member of thisinvention is used to transmit a force, specifically to provide a uniformcompacting force to a body of granular or powdered material. In theembodiment shown in FIGS. 9 through 12, the expandable member of thisinvention is adapted for use as a seal against differential pressure.Specifically, in this embodiment the expandable member is designed foruse with a testing device for applying pressure externally to aconnection between two tubular members to test the joint for adequacy ofseal.

In FIG. 9, the threaded ends (not shown) of tubular members 70 and 71are connected together by collar 72. After the two joints are connectedtogether, it is desirable in many instances to test the connectionbefore placing the connection in service. One way of testing suchconnections is to subject the connection to an external pressure of apredetermined amount. In order to conveniently provide such a test, asplit housing must be used that can be clamped around the connection andthen removed. Otherwise, the housing would have to be slipped down overthe pipe from one end, which in many cases would be awkward. Also, thethreaded connection often has a portion, such as collar 72, that islarger in diameter than the pipe and would create sealing problems.Therefore, the housing of the testing apparatus is split so that it canbe asembled around the connection and then removed after the test iscompleted.

In the embodiment shown, the housing includes sections 73 and 74 thatare semi-circular in cross section. The two sections are connectedtogether by hinge 75 which includes hinge pin 76, as shown in FIG. 10.When the two halves are brought together around the pipe, their freeends are connected by bolts 77 that extend through mating flanges 78 and79 that extend along the abutting edges of the housing sections. Eachhousing section has longitudinally spaced arcuate flanges that will formannular rings 80 and 81 at opposite ends of the housing to support aseal ring adjacent to the outer surface of pipe joints 70 and 71,respectively. A seal must also be provided between the two halves of thehousing where they abut along a line parallel to the longitudinal axisof the pipe.

As shown in FIG. 10, housing section 73 is provided with groove 82 toreceive a seal member to engage the abutting surface of section 74 ofthe housing. In the same way, section 74 has groove 83 for the samepurpose along the opposite longitudinal seal between the two housingmember.

To seal the housing, two expandable members constructed in accordancewith the method of this invention are provided. The two seal members areshown isometrically in FIG. 12. Seal member 84 has straight section 85for positioning in groove 83 of housing section 84. Integrally attachedthereto at opposite ends are semi-circular seal members 86 and 87. Theseportions of the seal are carried in the inwardly extending arcuateflanges on opposite ends of housing section 74 that for annular portions80 and 81. Seal ring 90 is shaped like seal ring 84. It has straightsection 91 that is located in groove 82 of housing section 73. It isintegrally connected at opposite ends to semi-circular portions 86 and87 that combine with portions 86 and 87 of seal member 84 to form acomplete seal between the end flanges 80 and 81 of the housing and theoutside surface of pipe joints 70 and 71. Means (not shown) similar tothe arrangement described above in connection with the embodiment ofFIG. 1 are provided to expand seal members 84 and 90 and provide a sealbetween the housing sections and between the housing and the pipe sothat pressure inside the housing can be built up to the desired point oftest connection 72.

As shown in FIGS. 9 and 11, semi-circular portions 86, 87, 92, and 93have semi-circular core sections 86a, 87a, 92a and 93a embedded therein,respectively. Here either the concave or the convex surface of the corescan be unattached to the elastomeric body of the member, since movingthe cores toward the surface to be sealed will accomplish the sameresult as moving only the elastomeric material. This is also true of theembodiments described in FIGS. 5 through 8 and of straight sections 85and 91 of the seals that have straight cores 85a and 91a. Straight coresections 85a and 91a are integrally connected at each end tosemi-circular core sections 86a and 87a and 92a and 93a, respectively.This allows one pressure to be supplied between the cores and theunattached portion of the body of the seal members through onepassageway (not shown), although more than one could be used if desired.

The pressure used to expand the seal rings of this invention need beonly enough to seal against the differential pressure to be placedinside the housing. This increases the life of the seal members. As soonas the test is completed pressure can be released from the cavities ofthe seal rings and the housing can be quickly and easily removed fromthe pipe.

In all of the embodiments described above, the core in the expandablemember of this invention has been generally symmetrical in shape. Theremay be occasions, however, when it would be desireable to apply theforce of the expandable member in varying amounts to different portionsof the material being compacted at various stages of pressurization ofthe expandable member. FIGS. 13 through 16 illustrate how this can beaccomplished by changing the cross-sectional shape of the core.

In FIG. 13, core 95 is thicker at one end than the other. Since, asshown, body 96 of elastomeric material is uniform in shape, this resultsin a thicker portion of elastomeric material between the core and thesurface to be pressured at one end than there is at the other. Also, theend of core 95 on the right hand side is closer to the end walls ofhousing 97 than it is at the other end. Thus, portion 96a on the lefthand end is thicker than portion 96b between the end of the core and thehousing on the right hand end. Thus, as pressure is applied to thecavity between the core and the body, portion 96b will offer lessresistance to movement than does portion 96a and relatively thin portion96c will move initially further toward the material being compacted thanwill thicker portion 96d at the left hand end. As the pressure buildsup, of course, the additional resistance to movement of the thickersections on the left hand end will be less and less effective to causethis portion to lag behind the right hand portion until, as shown inFIG. 16, the pressure has reached the point where the elastomer isacting like a liquid and substantially uniform pressure is being appliedto granular material 98. By causing the pressure to increase from theright hand side to the left hand side of the granular material, some ofthe material will be displaced in that direction and produce a taperedbody of compacted material.

From the foregoing, it will be seen that this invention is one welladapted to attain all of the ends of objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the method and apparatus.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the apparatus and method ofthis invention without departing from the scope thereof, it is to beunderstood that all matter herein set forth or shown in the accompanyingdrawings is to be interpreted as illustrative and not in a limitingsense.

The invention having been described, what is claimed is:
 1. A method ofmaking an expandable assembly for applying a force comprising:providingmold body means having a mold cavity therein, said mold body meansincluding at least one mold member having a mold cavity surface facinginto and partially defining said mold cavity and a bore opening throughsaid mold cavity surface; positioning a rigid core in said mold cavityin spaced relation to said mold cavity surface of said one mold member,said core having a first surface facing generally toward said moldcavity surface, a second surface facing generally away from said moldcavity surface, and a bore opening through said second surface;providing conduit means in said mold cavity communicativelyinterconnecting the bores of said one mold member and said core; placingan elastomeric material, in non-solid form, in said mold cavity insurrounding relation to said core; causing said elastomeric material tosolidify to a self-supporting elastomeric body with said core imbededtherein while permitting said elastomeric material to bond to said moldcavity surface and to said conduit means but preventing said elastomericmaterial from bonding to at least said second surface of said core,whereby a potential fluid cavity is formed between said elastomeric bodyand said second surface of said core for receiving fluid from saidconduit means to expand said elastomeric body away from said secondsurface of said core, and whereby said one mold member may provide atleast partial external support for said elastomeric body.
 2. The methodof claim 1 wherein said conduit means extends between said mold cavitysurface and said first surface of said core and serves to at leastpartially support said core on said one mold member during saidemplacing and solidifying of said elastomeric material.
 3. The method ofclaim 1 wherein said expandable assembly, including said one moldmember, said elastomeric body, said conduit means, and said core isemployed as a unit to form a compacting press for compacting powderedmaterial by expanding said fluid cavity to force said elastomeric bodyagainst such powdered material.
 4. The method of claim 3 wherein saidone mold member is used to form at least a portion of a rigid supportingframework of said compacting press.
 5. The method of claim 4 whereinsaid mold cavity surface is concave.
 6. The method of claim 5 whereinsaid one mold member is generally tubular and said mold cavity surfacecomprises the inner surface of said one mold member.
 7. The method ofclaim 1 wherein said elastomeric material comprises olyurethane.